1. Field of the Invention
The present invention relates to intraocular lenses to be implanted onto a natural or artificial lens in the eye to modify the existing lens system of the eye comprising the cornea and a natural or existing artificial lens. More particularly, the invention relates to an intraocular lens having either a substantially non-refractive configuration with a high minus portion at its center, or a substantially non-refractive prismatic or other diffractive configuration, and which is adaptable for implantation in the eye to modify the natural lens or an existing artificial lens to be adaptable to function as a teledioptic lens or diffractive lens, respectively.
2. Description of the Related Art
A normal ametropic eye includes a cornea, lens and retina. The cornea and lens of the normal eye cooperatively focus light entering the eye from a far point, i.e., infinity, onto the retina. However, an eye can have a disease known as macular degeneration which can greatly degrade vision.
Macular degeneration has become one of the leading causes of blindness in adults. This disease affects the central retinal area known as the macula which receives light focused by the cornea and lens and acute vision. Macular degeneration can lead to a gradual or sudden loss of vision to the level of 20/200 or less. Commonly, loss of vision only affects the central retinal area of about 0.25 to 4 square millimeters, and does not usually progress beyond this area, thereby leaving 95-99% of the retina unaffected. Thus, reading and driving vision can be lost, while peripheral vision remains intact.
U.S. Pat. Nos. 4,666,446 and 4,581,031, both to Koziol and Peyman, and both of which are incorporated by reference herein, each disclose intraocular lenses which are implanted in the eye in place of the natural lens to redirect the rays of light to minimize the adverse affect on vision caused by the macular degeneration of the eye. For example, U.S. Pat. No. 4,666,446 discloses an intraocular lens comprising a first portion including a diverging lens and a second portion including a converging lens. The converging lens provides the eye with substantially the same focusing ability of the natural lens prior to implantation of the intraocular lens. Thus, the eye will have decreased visual acuity due to the macular degeneration, but will also have unrestricted peripheral vision. The diverging lens, on the other hand, when combined with a converging lens positioned outside of the eye (e.g., a spectacle lens), provides a magnified image with increased visual acuity but a restricted visual field. Therefore, this type of intraocular lens creates teledioptic lens system, which provides the patient with the choice of unmagnified but peripherally unrestricted vision or magnified but peripherally restricted vision.
U.S. Pat. No. 4,581,031, discloses an intraocular lens including a convex portion and a prismatic portion. The combined convex/prismatic lens directs rays of light away from the center of the retina that has been damaged by macular degeneration, and focuses those rays onto an undiseased area of the retina, thus providing greater visual acuity.
As discussed above, U.S. Pat. Nos. 4,666,446 and 4,581,031 clearly disclose that it is known to use particular types of intraocular lenses in place of the natural lens to reduce the adverse affect of macular degeneration on vision. However, neither of the patents disclose that it is known to use an intraocular lens to modify an existing lens system in the eye, comprising the cornea and a natural or artificial lens already present in the eye, to create a lens system having the prismatic or teledioptic capabilities discussed above to correct for macular degeneration in the eye.
U.S. Pat. Nos. 5,098,444, 5,366,502, 5,358,520, and 4,932,971, as well as world patent application WO 94/07435, each disclose that it is known to attach a supplemental intraocular lens to an existing artificial intraocular lens to correct for ongoing degradation of vision. That is, if the ability of the eye to focus grows worse over time, instead of replacing the entire intraocular lens with a new intraocular lens having a different refractive power, a supplemental intraocular lens can be attached to the existing intraocular lens. This technique is less invasive and hence, less traumatic to the eye.
However, like U.S. Pat. Nos. 4,666,446 and 4,581,031, none of these patents discloses a supplemental intraocular lens that can be attached to the natural lens or an existing artificial lens to make the lens adaptable to function as a teledioptic or diffractive prismatic lens of the type described above. Accordingly, a continuing need exists for a supplemental intraocular lens having these capabilities.